Fix tactile switch wiring: GPIO22 to GND, show live pin level.

Clarify 4-pin foot pairing and debounce for bare pushbutton.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/button.h

@@ -8,3 +8,5 @@ bool button_poll_press();
 uint32_t button_count();
 void button_reset_count();
 bool button_is_down();
+/** 原始电平：1=HIGH，0=LOW（便于接线排查） */
+int button_raw_level();